Average gas rates for residential customers will drop nearly 6 percent compared with the average bills a year ago. However, electricity rates will rise about 2 percent compared with January 2012, PG&E said.

The January decline in gas bills will be offset somewhat by an increase anticipated for February. That increase is due to a pipeline safety upgrade approved by state regulators, PG&E said.

In February, after the changes in the various rates, the average residential customer who has combined gas and electricity service should see an overall decrease of $1.73 a month in their bills compared with what they were approximately a year ago, an analysis of the PG&E billing and rate estimates shows.

Natural gas rates are falling because wholesale costs have declined. Meanwhile, electricity rates are rising because of PG&E's costs to maintain and modernize its electricity system, as well as a state government mandate that obliges PG&E to buy more renewable energy for its power grid.

"These revenues help us serve customers by reducing the frequency of electrical outages, improving the responsiveness of our call centers, providing more convenient services and, above all, continuing to upgrade the safety

of our gas and electric operations," said Tom Bottorff, PG&E's senior vice president of regulatory affairs.

PG&E is under pressure to create a safer and more modern gas pipeline system in the wake of the lethal San Bruno explosion in 2010.

"Although electric and gas rates fluctuate from year to year, our average customer bills remain well below the national average," Bottorff said.

The average electricity bill will change in these ways: For PG&E customers using 550 kilowatt hours in a month, bills will average $91.60, up $2.29 from a year ago; for 850 kilowatt hours of usage, bills will average $188.05, up $3.82; for 1,200 kilowatt hours of usage, bills will average $307.13, up $5.59.

Gas bills for customers with average usage at 72 therms a month will total $77.47, a decline of $4.90 compared with a year ago.

The natural gas bill increases related to the pipeline upgrades should average 88 cents a month, although there are no guarantees because PG&E is constantly buying wholesale gas in the open markets, which can be volatile.